Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2011

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: FixedPoint[Cos, 1.0]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg119409] Re: FixedPoint[Cos, 1.0]
  • From: Dana DeLouis <dana.del at gmail.com>
  • Date: Thu, 2 Jun 2011 07:16:28 -0400 (EDT)

Hi.  I remember this use to work as per the documentation example in earlier versions.
As others have mentioned, the values cycle.

FixedPointList[Cos,1.0,91][[-3;;]]//FullForm
List[0.7390851332151605`,0.7390851332151608`,0.7390851332151605`]

Perhaps an alternative...

NestWhile[Cos[#]&,1.0,UnsameQ,All]//FullForm
0.7390851332151605`

If we add an extra 2 loops (1000 for safety or max loops) we see the same cycle.

t=NestWhileList[Cos[#]&,1.0,UnsameQ,All,1000,2];

t[[-3;;]]//FullForm

List[0.7390851332151605`,0.7390851332151608`,0.7390851332151605`]

= = = = = = = = = =
HTH  : >)
Dana DeLouis
Mac, Math 8


On May 31, 7:49 am, J Siehler <jsieh... at gmail.com> wrote:
> My numerical analysis students this past term pointed out to me that
> the command
>
> FixedPoint[Cos, 1.0]
>
> which is the first example in the Information for FixedPoint doesn't
> ever finish running (or, not in any reasonable amount of time).  We
> tried this on serveral versions of Mathematica (6.x, 7.x, and 8.x),
> all on OS X, and got the same nonresult.
>
> It can be forced by specifying something like FixedPoint[Cos, 1.0,
> SameTest -> (Abs[#1 - #2] < 10^-10 &)] or FixedPoint[Cos, 1.0, 40],
> but it seems like that should be unnecessary, and the form given in
> the documentation should work.  Can anybody else confirm this
> behavior?  Am I missing something totally obvious here?


  • Prev by Date: Re: Akima-Interpolation
  • Next by Date: Re: Dt@x@1
  • Previous by thread: Re: FixedPoint[Cos, 1.0]
  • Next by thread: Re: FixedPoint[Cos, 1.0]